PROJECT SUMMARY The CGIBD Gnotobiotic Core, an integral Center component since 1988, is a highly utilized resource that provides CGIBD members with germ-free (sterile), selectively colonized and fecal transplanted mice to precisely study host-environmental interactions and bacterial functions. This world-class facility allows CGIBD members, their trainees and collaborators to perform cutting edge investigations using wild-type (WT) and genetically engineered transgenic, knockout and reporter gnotobiotic mice in the absence of microbiota [germ- free (GF)] or colonized with single bacterial species, including gene deletion/complemented mutants, defined consortia of murine or human bacterial species or transfer complex fecal microbial communities from experimental mice or humans (microbiologically humanized mice) with dysbiosis to study disease pathogenesis. The two Gnotobiotic Core branches, one at UNC-Chapel Hill and the other at the NC State University College of Veterinary Medicine provide GF or gnotobiotic mice and associated technical services, to CGIBD members, associate members, and new investigators at each location. We maintain 28 GF mouse strains and lines, including WT, knockout, transgenic, and reporter mice. The specific aims of the Core are: 1) Provide GF or selectively colonized (gnotobiotic) WT and mutant mice, their tissues and cells. 2) Derive additional GF WT and genetically engineered mouse strains. 3) Consult with investigators to optimize experimental design and implementation and provide technical services. 4) Support studies for new investigators to generate key data for grant applications. 5) Develop a library of fully characterized bacterial strains and complex human and murine fecal communities to facilitate reproducible results in gnotobiotic studies. This facility and the combined expertise of the Directors, Balfour Sartor, UNC-CH and Sue Tonkonogy, NCSU provide Center members with an unparalleled resource to perform innovative, mechanistic research to identify microbial contributions to GI homeostasis, disease, injury, and repair.